If $x \bigtriangledown y = 2x-7$ and $x \otimes y = x(y-6)$, find $(3 \otimes 5) \bigtriangledown -1$.
Answer: First, find $3 \otimes 5$ $ 3 \otimes 5 = 3(5-6)$ $ \hphantom{3 \otimes 5} = -3$ Now, find $-3 \bigtriangledown -1$ $ -3 \bigtriangledown -1 = (2)(-3)-7$ $ \hphantom{-3 \bigtriangledown -1} = -13$.